Single-Molecule Magnets: A Family of Mn^III/Ce^IV Complexes with a [Mn₈CeO₈]¹²⁺ Core

Abstract

Four heterometallic, enneanuclear Mn8Ce clusters [Mn8CeO8(O2CMe)12(H2O)4] (4), [Mn8CeO8(O2CMe)12(py)4] (5), [Mn8CeO8(O2CPh)12(MeCN)4] [Mn8CeO8(O2CPh)12(dioxane)4] (6), and [Mn8CeO8(O2CCHPh2)12(H2O)4] (7) have been prepared by various methods. Their cores are essentially isostructural and comprise a nonplanar, saddlelike [MnIII8O8]8+ loop containing a central CeIV ion attached to the eight micro3-O2- ions. Peripheral ligation around the [Mn8CeO8]12+ core is provided by eight micro- and four micro3-O2CR- groups. Terminal ligation on four MnIII atoms is provided by H2O in 4 and 7, pyridine in 5, and MeCN/dioxane in 6. Solid-state magnetic susceptibility studies, fits of dc magnetization vs field and temperature data, and in-phase ac susceptibility studies in a zero dc field have established that complexes 4, 5, and 7 possess S=16, S=4 or 5, and S=6+/-1 spin ground states, respectively, but in all cases there are very low-lying excited states. The large variation in the ground-state spins for this isostructural family is rationalized as due to a combination of weak exchange interactions between the constituent MnIII atoms, and the presence of both nearest-neighbor and next-nearest-interactions of comparable magnitudes. Magnetization vs applied dc field sweeps on single crystals of 4.4H2O and 7.4H2O.3MeCN.2CH2Cl2 down to 0.04 K have established that these two complexes are new single-molecule magnets (SMMs). The former also shows an exchange-bias, a perturbation of its single-molecule properties from very weak intermolecular interactions mediated by hydrogen-bonding interactions with lattice-water molecules of crystallization.

Homo‐ and Heterovalent Polynuclear Cerium and Cerium/Manganese Aggregates

“…6 Mn III 4 (m 4 -O) 4 (m 3 -O) 4 (O 2 C t Bu) 12 (ea) 4 4 (m 3 -O) 8 (pye) 4 3 (m 3 -O) 3 (m 3 -OH) 2 (m-OH)(bdea) 4 (O 2 C t Bu) 9.5 -(NO 3 states [10]. High-valent Mn or Ce oxo species are of relevance to a large number of areas such as chemistry, biology, industry, and the environment because of their ability to oxidize both inorganic and organic substrates [11 -18].…”

“…Recently, Fukuzumi, Nam, and co-workers employed Ce IV as a oneelectron oxidant in the generation of mononuclear non-heme Fe IV oxo complexes and in the catalytic oxidation of organic substrates with H 2 O as an O-atom source [20]. Despite these properties of Mn IV and Ce IV compounds, it is rather surprising that there are still rather few reports of Ce IV -containing heterometallic complexes [9]. Aminoethanol (¼ ethanolamine) ligands are an attractive class of ligands in view of their extensively documented ability to bridge metal ions to afford a variety of complexes [21].…”

Synthesis, Antioxidant Activity and Fluorescence Properties of Novel Europium Complexes with (E)-2- or 4-hydroxy-N'-[(2-hydroxynaphthalen-1-yl)methylene]benzohydrazide Schiff Base

“…[7][8][9][10][11] Organic rare earth complexes have garnered growing interest due to their potential application as fluorescent probes, labels in biological immunoassay applications, as optical amplifiers 12,13 and as active central species in photoluminescent materials. 14,15 Due to the unique photophysical and photochemical properties of rare earths complexes which exhibit potential to be harnessed in the development of new photodynamic therapies, they offer exciting opportunities to elucidate the structural features of nucleotides such as DNA.…”

A New Family of Homo‐ and Heterometallic Manganese Complexes at High Oxidation States Derived from the Oxidation of MnII with CeIV: Syntheses, Structures, and Magnetic Properties

“…An alternative fit with S = 8 or 6 has been done but no improved results were obtained. 4 ] (S = 4 or 5), [24] which is probably as a result of the differences in the crystal symmetry.…”